A. Field of the Invention
The present invention relates generally to a preservative or anti-microbial system that can be used to inhibit the growth of microorganisms. The preservative or anti-microbial system can be used in a variety of applications (e.g., in topical formulations such as cosmetic or pharmaceutical formulations, cleansing or disinfectant formulations for hard surfaces or for skin or for skin wounds, food formulations, etc.). The preservative or anti-microbial system includes a mixture of esters from glycerol and salicylic acid.
B. Description of Related Art
There are several preservative/anti-microbial systems currently available. Examples of such systems generally include parabens (e.g., methylparaben, ethylparaben, propylparaben, benzylparaben, butylparaben, etc.), which are useful against gram-positive bacteria, isopropynylbutylcarbamate (IPBC), which is useful against mold, imidazolidinyl urea, which is used full against gram-negative bacteria, methylisothiazolinone (MIT), which is useful against gram-negative bacteria, chlorphenesin, which is useful against mold, benzoic acid, which is useful against gram-positive bacteria, yeast, and mold, and caprylyl glycol, which is useful against gram negative bacteria. While these systems are useful in inhibiting the growth of various types of microorganisms, several have drawbacks ranging from toxicity to difficulties in using them to formulate compositions.
One potential alternative to chemical preservatives is to use natural ingredients. However, such ingredients can be costly, not as effective, and can actually be caustic or irritating to skin if used in effective amounts. For instance, Amipreserve by Alban Muller International is a pure natural salicylic acid that is extracted from wintergreen leaves. The maximum recommended amount of Amipreserve to include in a given formulation is 0.5 wt % due to the caustic effects of salicylic acid—in particular the free carboxylic acid group of this molecule. Therefore, additional preservatives or anti-microbial agents are needed in the formulation to effectively inhibit microorganism growth.
As another example, caprylyl glycol is difficult to use with emulsions. In particular, caprylyl glycol can destabilize emulsions by interfering with the interface between the continuous and discontinuous phases of said emulsion. Therefore, it can be difficult to formulate with and oftentimes it has to be added to the formulation post emulsification. Such a procedure adds additional process steps, complexity, and costs to preparing the emulsion.
Oftentimes, in order to produce a broad spectrum preservative or anti-microbial system, several different types of preservatives have to be combined. This increases the costs of the preservative system, adds additional ingredients to the formulation, and can potentially affect the stability of the formulation.